Calcium Sulfate Crystal Morphology Control And Catalytic Luminescence Sensing Performance Study

The crystal ofα-CaSO₄·0.5H₂O has been widely used in industries such as biomedicine,construction,and decoration due to its good biocompatibility,size stability,and strong tensile strength.The main component of gypsum is CaSO₄·2H₂O,and how to convert it intoα-CaSO₄·0.5H₂O crystals economically and efficiently has become a hot area of technological innovation for gypsum resource utilization.Therefore,the corresponding preparation process technology and theoretical basic research have become very urgent.In this paper,CaSO₄·2H₂O was used as raw material to optimize the reaction processes of hydrothermal method and atmospheric pressure chlorine-free salt solution method,to explore the influencing factors of crystal preparation and the regulation of crystal morphology by crystal shape modifiers,and to provide theoretical guidance for the research of newα-CaSO₄·0.5H₂O crystals;and CaSO₄ was used as a sensitive material to study its catalytic luminescence sensing performance and explore new application directions of CaSO₄.The main work of the paper is as follows:（1）The hydrothermal method was used to investigate the effect of process conditions（reaction temperature and time）on the morphology and size ofα-CaSO₄·0.5H₂O crystals using CaSO₄·2H₂O as the starting material.The optimal process conditions were determined to be a slurry concentration of 2%,a reaction temperature of 160℃,and a reaction time of 6 hours.The effects of Mg²⁺and Al³⁺concentrations on the morphology and size ofα-CaSO₄·0.5H₂O crystals were systematically studied.The results showed that in the presence of low concentrations of Mg²⁺,the diameter ofα-CaSO₄·0.5H₂O crystals was smaller,and the aspect ratio was higher.Al³⁺had a strong inhibitory effect on the growth ofα-CaSO₄·0.5H₂O crystals along the c-axis,resulting in rod-shaped or spindle-shaped crystals.（2）Theα-CaSO₄·0.5H₂O crystals were prepared using a chloride-free solution method under atmospheric pressure,with CaSO₄·2H₂O as the starting material.The process conditions（reaction temperature,reaction time,solution p H,and liquid-to-solid ratio）were optimized,and the optimal process parameters were determined to be a Na₂SO₄salt solution concentration of 12.5%,a p H of 7,a reaction temperature of 97,a stirring speed of 100 rpm,and a liquid-to-solid ratio of 5:1.Under the optimized conditions,the effects of sodium succinate,sodium citrate,and EDTA as crystal morphology modifiers on the morphology and size ofα-CaSO₄·0.5H₂O crystals were studied.The experimental results showed that sodium succinate and EDTA had weak control over the morphology and size of the crystals,only affecting the size of the crystals and having little effect on the morphology.Sodium citrate had a more significant effect on the control ofα-CaSO₄·0.5H₂O crystals,with crystals changing from whisker-like to columnar at a concentration of 10 m M,forming hexagonal shapes at 20 m M,and irregular shapes at 50m M.The citrate ion had an electron effect with Ca²⁺,and it chemically adsorbed onto the surface of the crystal.（3）α-CaSO₄·0.5H₂O crystals were prepared from CaSO₄·2H₂O,and were transformed into anhydrous calcium sulfate crystals by high-temperature calcination at500.The anhydrous calcium sulfate crystals were used as a sensitive material to prepare a catalytic luminescence sensor for the detection of organic volatile gases.It was found that the sensor exhibited a strong response to diethyl ether gas,and the optimal working conditions for the sensor were a wavelength of 440 nm,a temperature of 320,and a flow rate of 350 m L/min.Under these conditions,quantitative analysis of diethyl ether gas was performed,and the experimental results showed that the catalytic luminescence intensity exhibited a good linear relationship with diethyl ether gas concentration in the range of 0.5m M-25 m M,with an R²=0.9960 and a detection limit of 4.3×10^-5M（S/N=3）.The sensor showed weak or no response to 10 common VOCs,including ethanol.To evaluate the stability of the sensor,measurements were performed continuously for seven days,and the relative deviation was only 1.9%.